1. Field of the Invention
The present invention relates to an X-ray imaging device and an X-ray imaging method, by which a plurality of two-dimensional images is acquired by performing imaging during the rotation of an X-ray generation unit and an X-ray detection unit around a sample as a rotation center, and a three-dimensional soft tissue image or the like of the sample is acquired by performing a reconstruction of the two-dimensional images.
2. Description of the Related Art
The X-ray imaging device equips a C arm. The C arm is provided with an X-ray generation unit and an X-ray detection unit facing one another. There has been proposed a technique of acquiring a three-dimensional soft tissue image of a sample with the use of the X-ray imaging device. The soft tissue image of the sample acquired according to such technique shows soft tissues of internal organs, etc., inside the sample such as tissues having low X-ray absorption. It has been understood as that the soft tissue image is capable of showing, for example, a difference of a substance X-ray absorption coefficient by 10 H.U. in approximate with a CT value expressed in a relative value from a reference substance.
The X-ray imaging device rotates the X-ray generation unit and the X-ray detection unit around a sample as a rotation center by rotating the C arm. The X-ray imaging device images at every rotary move by predetermined angle while rotating the X-ray generation unit and the X-ray detection unit. The X-ray imaging device acquires a plurality of two-dimensional images by performing the imaging at every rotary movement, and reconstructs a three-dimensional soft tissue image of the sample from the two-dimensional images. For the reconstruction, a three-dimensional soft tissue image is reconstructed by applying the reconstruction theory such as Feldkamp method, or the like. In order to reconstruct the three-dimensional soft tissue image, it is necessary to acquire about 400 frames of two-dimensional images by imaging from about 400 directions of an imaging angle direction.
While surgical operation, the three-dimensional soft tissue image of the sample acquired by the X-ray imaging device is shown on a display. When there is confirmed, for example, a bleeding from vessel, a treatment to stop the bleeding is carried out. In this case, there is a demand to identify a bleeding blood vessel in the sample and observe the blood vessel image and the soft tissue image by overlaying them for a display.
In order to acquire the blood vessel image, it is necessary to inject a contrast agent into a blood vessel and obtain the flow of the contrast agent by an X-ray imaging. For the blood vessel image, as shown in FIG. 17 for example, the rotation of X-ray generation unit and X-ray detection unit is initiated under a condition of without a contrast where the contrast agent is not injected. At this time, the X-ray generation unit and the x-ray detection unit start rotate from a rotation start angle position s to a rotation end angle position e around a sample 1 as a rotation center within the imaging range of θ. The imaging is performed at imaging angle positions k1, k2, . . . , kn, respectively, whereat the X-ray generation unit and the X-ray detection unit step each by a predetermined angle. Accordingly, there can be obtained, for example, 400 directions of a two-dimensional image 2 without a contrast. The rotation angle of the imaging range θ is obtained by adding 180° with a Fan angle F. Thus obtained 400 frames of a two-dimensional image 2 without a contrast are recombined to acquire a three-dimensional soft tissue image 3 showing soft tissues.
Alternatively, in the presence of a contrast where the contrasting agent is injected, the X-ray generation unit and the x-ray detection unit are rotated around the sample 1 as a rotation center within the imaging range of θ. Then, the imaging is performed at imaging angle positions k1, k2, . . . , kn, respectively, whereat the units step each by predetermined angle as above, thereby obtaining, for example, 400 frames of a two-dimensional image with a contrast.
Next, images 4 which are the subtraction between 400 frames of the two-dimensional image 2 without a contrast and 400 frames of the two-dimensional image 3 with a contrast are obtained. The subtraction images 4 are recombined to acquire a three-dimensional blood vessel image 5 showing blood vessels.
However, since it is necessary to acquire total 800 frames of images, which are 400 frames of a two-dimensional image 2 without a contrast and 400 frames of a two-dimensional image with a contrast, such to acquire the blood vessel image 5, there may be a possibility of increase dose against the sample 1.
An example of the X-ray imaging device is disclosed in JP-A-2005-80285.